Despite recognizing the "obvious consumer appeal" of the technology, the team insisted that they have developed a "remarkable piece of code and an unusual conceptual exploration of the virtual and physical worlds".

They are now developing applications for the technology and their research will be presented in detail in the Association for Computing Machinery's (ACM) Transactions on Graphics, and at the ACM SIGGRAPH conference on August 7.

"In animation you're not necessarily trying to model the physical world perfectly; the model only has to be good enough to convince your eye," explained lead author and Harvard graduate Moritz Bächer.

"In a virtual world, you have all this freedom that you don't have in the physical world. You can make a character so anatomically skewed that it would never be able to stand up in real life, and you can make deformations that aren't physically possible.

"You could even have a head that isn't attached to its body, or legs that occasionally intersect each other instead of colliding."

The technology for printing fully 3D objects is gradually coming into people's reach, offering a way to take the virtual into the physical world and also potentially cut out the heavy cost of shipping consumer goods.

For example, it is thought that future shopping could involve users selecting the item they want and then having it printed in 3D in front of them to their exact specifications.

The Harvard team said that bringing a virtual character into the physical world "turns the traditional animation process on its head", involving a process of "reverse rendering", in which the image that is on screen must be adapted to the real world.

Bächer and his co-authors demonstrated their new method by taking characters from Spore, an evolution-simulation game from Electronic Arts that involves users creating strange creatures from limbs, eyes and body segments.

As with most computer animation, the characters in Spore are skins, or meshes of polygons, which are manipulated to create an invisible skeleton.

"As an animator, you can move the skeletons and create weight relationships with the surface points," said Bächer, "but the skeletons inside are nonphysical with zero-dimensional joints; they're not useful to our fabrication process at all. In fact, the skeleton frequently protrudes outside the body entirely."

Joining other experts from US and Germany, Bächer developed a software tool that identifies the locations of the figure's joints and then optimises the size and location of those joints for the physical world.

The software uses a series of optimisation techniques to generate the best possible model, incorporating hinges and ball-and-socket joints to make the figures fully posable.

It also models the skin textures in the resulting 3D print, translating the surface details to make the model look more realistic and reflective of the virtual version.

"With an animation, you always have to view it on a two-dimensional screen, but this allows you to just print it and take an actual look at it in 3D," says Bächer.

"I think that's helpful to the artists and animators, to see how it actually feels in reality and get some feedback. Right now, perhaps they can print a static scene, just a character in one stance, but they can't see how it really moves.

"If you print one of these articulated figures, you can experiment with different stances and movements in a natural way, as with an artist's mannequin."

The one limitation of Bächer's model is that it does not allow deformations beyond the joints, so stretchable bodies are not possible, although that could achieved in the future.

For example, the team was able in 2010 to replicate an entire flip-flop using a multimaterial 3D printer, mimicking the elasticity of the original foam rubber and cloth.

Harvard has filed a patent application for the new 3D printing system and is working with the Pfister lab on ways to commercialize the technology by licensing it to an existing company or by forming a startup.

They have identified immediate of areas of focus including "cloud-based services for creating highly customized, user-generated products, such as toys", along with ways to enhance existing animation and 3D printer software with the capabilities developed by Bächer.

It is also hoped that in future a "3D print" button could be developed for inclusion in games and other services.

"Perhaps in the future someone will invent a 3D printer that prints the body and the electronics in one piece," Bächer said.

"Then you could create the complete animated character at the push of a button and have it run around on your desk."